Salty Tomatoes

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Unless you can pick your tomatoes so irresistibly table-ready in the garden that you gobble at least two while gathering some for supper, you probably add a little sprinkle of salt to sliced tomatoes. It brightens the flavor. So why not grow plants in salty soil so they can absorb it as they grow?

Don’t be silly, everybody knows most plants die in salty soil. And planet-wide, that’s the problem. We’re running out of clean, salt-free soil. Science News says salty soil ruins farming potential in more than a THIRD of the world’s irrigated lands. Every release of irrigation water adds a bit of salt to the land. Over the years, it becomes too saline for food plants.

Scientists are looking at various ways of helping. The most obvious, of course, is to use the oceans: build as many desalinization facilities as possible; but so long as most countries put vast amounts of money into weapons to kill each other with, few can afford that costly process.

Researchers have been trying for years to develop crops that could thrive in salty soils. Now, Eduardo Blumwald and colleagues at the University of California are making progress. They genetically altered tomato plants to grow well in salt water. That would not only give farmers a salable crop to grow on saline land, the plants pull much of the salt up into their leaves, thus cleaning the soil for use by other crop plants.

The researchers started experimenting with a plant that’s been used for years in botanic experiments, as it’s cheap and easy to grow – Arabidopsis thaliana. By 1999, they began to see success. They needed to take just one active gene, put it into Arabidopsis, and behold – the little weed grew well in salt water. The gene encodes a protein that imprisons sodium in sacs called vacuoles in the plant cells, so the salt can’t damage them. Many salt-tolerant weeds use this trick. Others, including most of our developed crop plants, have turned that gene off.

The botanists duplicated the weed experiment with tomatoes, and last August, announced success. Crops usually fail if they’re in a solution with 50 millimolar of salt. (Millimolar is a special measure they use for salt). The experimental tomatoes did fine in a 200 millimolar solution. They don’t taste salty because most of the salt goes up into the leaves. Blumwald says the tomatoes tasted great. Other scientists point out that crops using this system must perform well in other ways also. Tomatoes, for instance, must ripen uniformly, and have tough enough skin so they can be handled commercially.

No one can predict how successful they’ll be with other plants, though Blumwald says he’s already succeeded with canola (rapeseed plant). Still, tomatoes have a simpler genome than many other food crops, such as wheat, so the gene-switch is probably snot a universal solution.

This is Ruth Page, talking with you about one way in which science may be able to make use of saline soils.

–Ruth Page is a writer and former editor of a weekly newspaper and a national gardening magazine.

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